Exercise and physical fitness are a permanent part of life for millions of people in today's world. While some forms of exercise are more vigorous than others, every form of exercise brings with it the possibility of injury. Accompanying the steady increase in fitness activities over the last decade are an increasing number of musculoskeletal injuries being reported. Many injuries of this kind require surgical restoration of the damaged muscles, tendons, ligaments and other body components especially when a body joint such as the knee, elbow, shoulder, ankle, or wrist is involved. Following surgery to repair a body joint, the patient typically returns to normal activity only after enduring a long and structured program of rehabilitation. The rehabilitation process generally involves constant stabilization and support of the injured joint along with a gradually demanding program of therapy and exercise to strengthen the surrounding muscles and return flexibility to the repaired ligaments. Most programs consist of simple flexion and extension of the body joint and some applied resistance as the injured joint permits. These rehabilitative exercises are customarily performed within a controlled line and range of motion with the resistance level being increased over time. This is to help prevent any further injury and to prevent the joint from bearing too much stress before it is ready.
The stability and mobility of the injured joint is often controlled by the constant wearing of a brace or similar appliance generally consisting of coupled frames made up of an upper and lower section and a pivot joint. These braces are designed to be carried entirely by the body with the pivot joint generally coinciding with the anatomical pivot axis of the associated body joint. Throughout the beginning stages of the recovery, the patient may be required to wear a stabilizing brace during all times of activity, even for normal movement. Then, as the injured joint is strengthened, the brace becomes necessary only for more strenuous exercises. Although the bracing devices do provide stability and thus help facilitate the recovery of the joint, the brace itself has no muscle building effects.
Normally, the rehabilitative treatment program is designed and administered by a physical therapist often with all of the exercises being presided over at a special facility or clinic utilizing sophisticated, complex equipment that requires supervision and instruction. Possible machines found in these specialized clinics are disclosed in U.S Pat. Nos. 4,436,303 to McKillip (1984), 5,020,797 to Burns (1991), and 5,074,549 to Harvey (1991). With this type of program the patient must make special considerations to deal with travel and time conveniences in order to complete a proper recovery. Even when patients are allowed to preside over some or all of the exercises on their own, the recommended exercises are often inefficient and awkward to perform, such as lifting sandbags, working out with surgical tubing, and self-administered stretching. As a consequence of these burdens, physical therapy, one of the most important steps for the adequate recovery of the injured joint, is often missed or performed improperly, which leaves the joint unstable and more susceptible to reinjury. An incomplete or poorly followed program often leads to a poor or incomplete recovery.
Some more appropriate appliances have been developed for exercising and rehabilitating injured joints. Such devices typically include an upper and lower arm or section rotationally connected with a pivot joint assembly. These devices are designed to be suitably attached to the body in conjunction with the injured joint and to utilize a resistance mechanism to bias the relative movement of the pivot arms and thus impart a resistance force against movement of the body joints. Examples of such devices are disclosed in U.S. Pat. Nos. 3,976,057 to Barclay (1976), 4,718,665 to Airy and Kadavy (1988), 4,801,138 to Airy and Kadavy (1989), and 5,013,037 to Stermer (1991), as well as 5,052,375 to Stark (1991), 5,052,379 to Airy and Kadavy (1991), 5,116,296 to Watkins (1992) and 5,135,468 to Meissner (1992). While they are adapted to be mounted on the body, some of these devices are still too cumbersome to be worn continually during normal activity and some do not allow any adjustability of the resistance mechanism tension level or its angle of equilibrium. The ability to control the angle at which the resistance mechanism is in equilibrium allows the muscles used for flexion and the muscles used for extension of the joint to be exercised differently. Thus, depending on the injury, either the flexion or the extension of the joint can be emphasized and in varying amounts. The resistance tension level should be adjustable to control the force of resistance applied to the joint. Those devices which do possess adjustability make it awkward and inefficient to change their setup. The apparatus in U.S. Pat. No. 5,052,379 to Airy and Kadavy (1991) even necessitates removing and changing certain parts. The adjustable devices are also extremely complex and require elaborate and intricate manufacturing procedures such as those in U.S. Pat. Nos. 5,052,375 to Stark (1991) and 5,116,296 to Watkins (1992). The nature of their design also dictates that these adjustable rehabilitative devices be manufactured as a whole unit thus eliminating the possibility of quickly adapting the concept to a wide range of brace and pivot joint designs.